Re: [PATCH] module: clean-up for module_memory

[Christophe Leroy]

Le 09/02/2023 à 18:56, Song Liu a écrit :
> Three changes here:
> 
> 1. Shorter variable names in arch/arc/kernel/unwind.c:unwind_add_table, to
>     make it easier to read.
> 2. Rewrite free_mod_mem() so it is more obvious that MOD_DATA need to be
>     freed last.
> 3. Clean up the use of CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC.
> 
> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> Signed-off-by: Song Liu <song@xxxxxxxxxx>
> 
> ---
> 
> This is the follow up patch on top of [1]. I would recommend fold this
> into [1].

With this patch folded into [1],

Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

> 
> [1] https://lore.kernel.org/linux-modules/20230207002802.2514802-1-song@xxxxxxxxxx/T/#u
> ---
>   arch/arc/kernel/unwind.c | 15 ++++------
>   kernel/module/main.c     | 61 +++++++++++-----------------------------
>   2 files changed, 22 insertions(+), 54 deletions(-)
> 
> diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
> index 933451f4494f..9270d0a713c3 100644
> --- a/arch/arc/kernel/unwind.c
> +++ b/arch/arc/kernel/unwind.c
> @@ -369,8 +369,8 @@ void *unwind_add_table(struct module *module, const void *table_start,
>   		       unsigned long table_size)
>   {
>   	struct unwind_table *table;
> -	struct module_memory *mod_mem_core_text;
> -	struct module_memory *mod_mem_init_text;
> +	struct module_memory *core_text;
> +	struct module_memory *init_text;
>   
>   	if (table_size <= 0)
>   		return NULL;
> @@ -379,14 +379,11 @@ void *unwind_add_table(struct module *module, const void *table_start,
>   	if (!table)
>   		return NULL;
>   
> -	mod_mem_core_text = &module->mem[MOD_TEXT];
> -	mod_mem_init_text = &module->mem[MOD_INIT_TEXT];
> +	core_text = &module->mem[MOD_TEXT];
> +	init_text = &module->mem[MOD_INIT_TEXT];
>   
> -	init_unwind_table(table, module->name,
> -			  mod_mem_core_text->base, mod_mem_core_text->size,
> -			  mod_mem_init_text->base, mod_mem_init_text->size,
> -			  table_start, table_size,
> -			  NULL, 0);
> +	init_unwind_table(table, module->name, core_text->base, core_text->size,
> +			  init_text->base, init_text->size, table_start, table_size, NULL, 0);
>   
>   	init_unwind_hdr(table, unw_hdr_alloc);
>   
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index c598f11e7016..2724bc1b9a90 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -927,26 +927,17 @@ static ssize_t store_uevent(struct module_attribute *mattr,
>   struct module_attribute module_uevent =
>   	__ATTR(uevent, 0200, NULL, store_uevent);
>   
> -#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
> -
> -static ssize_t show_coresize(struct module_attribute *mattr,
> -			     struct module_kobject *mk, char *buffer)
> -{
> -	return sprintf(buffer, "%u\n", mk->mod->mem[MOD_TEXT].size);
> -}
> -
> -#else
> -
>   static ssize_t show_coresize(struct module_attribute *mattr,
>   			     struct module_kobject *mk, char *buffer)
>   {
> -	unsigned int size = 0;
> +	unsigned int size = mk->mod->mem[MOD_TEXT].size;
>   
> -	for_class_mod_mem_type(type, core)
> -		size += mk->mod->mem[type].size;
> +	if (!IS_ENABLED(CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC)) {
> +		for_class_mod_mem_type(type, core_data)
> +			size += mk->mod->mem[type].size;
> +	}
>   	return sprintf(buffer, "%u\n", size);
>   }
> -#endif
>   
>   static struct module_attribute modinfo_coresize =
>   	__ATTR(coresize, 0444, show_coresize, NULL);
> @@ -1170,17 +1161,11 @@ void __weak module_arch_freeing_init(struct module *mod)
>   {
>   }
>   
> -#ifdef CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
>   static bool mod_mem_use_vmalloc(enum mod_mem_type type)
>   {
> -	return mod_mem_type_is_core_data(type);
> -}
> -#else
> -static bool mod_mem_use_vmalloc(enum mod_mem_type type)
> -{
> -	return false;
> +	return IS_ENABLED(CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC) &&
> +		mod_mem_type_is_core_data(type);
>   }
> -#endif
>   
>   static void *module_memory_alloc(unsigned int size, enum mod_mem_type type)
>   {
> @@ -1199,34 +1184,21 @@ static void module_memory_free(void *ptr, enum mod_mem_type type)
>   
>   static void free_mod_mem(struct module *mod)
>   {
> -	/* free the memory in the right order to avoid use-after-free */
> -	static enum mod_mem_type mod_mem_free_order[MOD_MEM_NUM_TYPES] = {
> -		/* first free init sections */
> -		MOD_INIT_TEXT,
> -		MOD_INIT_DATA,
> -		MOD_INIT_RODATA,
> -
> -		/* then core sections, except rw data */
> -		MOD_TEXT,
> -		MOD_RODATA,
> -		MOD_RO_AFTER_INIT,
> -
> -		/* rw data need to be freed last, as it hosts mod */
> -		MOD_DATA,
> -	};
> -	int i;
> -
> -	BUILD_BUG_ON(ARRAY_SIZE(mod_mem_free_order) != MOD_MEM_NUM_TYPES);
> -
> -	for (i = 0; i < MOD_MEM_NUM_TYPES; i++) {
> -		enum mod_mem_type type = mod_mem_free_order[i];
> +	for_each_mod_mem_type(type) {
>   		struct module_memory *mod_mem = &mod->mem[type];
>   
> +		if (type == MOD_DATA)
> +			continue;
> +
>   		/* Free lock-classes; relies on the preceding sync_rcu(). */
>   		lockdep_free_key_range(mod_mem->base, mod_mem->size);
>   		if (mod_mem->size)
>   			module_memory_free(mod_mem->base, type);
>   	}
> +
> +	/* MOD_DATA hosts mod, so free it at last */
> +	lockdep_free_key_range(mod->mem[MOD_DATA].base, mod->mem[MOD_DATA].size);
> +	module_memory_free(mod->mem[MOD_DATA].base, MOD_DATA);
>   }
>   
>   /* Free a module, remove from lists, etc. */
> @@ -2211,8 +2183,7 @@ static int move_module(struct module *mod, struct load_info *info)
>   		if (!(shdr->sh_flags & SHF_ALLOC))
>   			continue;
>   
> -		dest = mod->mem[type].base +
> -			(shdr->sh_entsize & SH_ENTSIZE_OFFSET_MASK);
> +		dest = mod->mem[type].base + (shdr->sh_entsize & SH_ENTSIZE_OFFSET_MASK);
>   
>   		if (shdr->sh_type != SHT_NOBITS)
>   			memcpy(dest, (void *)shdr->sh_addr, shdr->sh_size);